Method of fabricating nano wire and nano wire complex

ABSTRACT

Disclosed are a method of fabricating a nano wire and a nano wire complex. The method of fabricating a nano wire includes forming a plurality of seed particles by allowing a first ion to react with a second ion in a solvent, and forming a metallic nano wire by adding and heating a metallic compound in the solvent.

TECHNICAL FIELD

The embodiment relates to a method of fabricating a nano wire and a nanowire complex.

BACKGROUND ART

A transparent electrode including transparent material has been appliedto various electronic products such as a display device, a solar cell,and a mobile device. Researches and studies on a nano wire, which has awire-shape structure in a nano-meter size, as the transparent conductivematerial for the transparent electrode, have been actively carried out.

Since the nano wire has superior electrical conductivity, flexibility,and transmittance, the transparent electrode can represent superiorcharacteristics. However, nano wires are easily aggregated during thereaction process, so that nano-particles are formed. Accordingly, thenano wire may not be easily fabricated. As a result, the product yieldof the nano wire is significantly lowered to about 10%, so that thepractical use of the nano wire may be difficult. Further, materials suchas catalysts used to accelerate the reaction of forming the nano wireremain on the surface of the nano wire, so that the surface oxidation orthe surface corrosion of the nano wire may occur, or the electricalconductivity may be degraded.

DISCLOSURE OF INVENTION Technical Problem

The embodiment provides a long thin wire.

Solution to Problem

A method of fabricating a nano wire according to the embodiment includesforming a plurality of seed particles by allowing a first ion to reactwith a second ion in a solvent, and forming a metallic nano wire byadding and heating a metallic compound in the solvent.

According to the embodiment, the first ion may be a metallic ion, andthe second ion may be a halogen ion.

According to the embodiment, the seed particles may include a metalequal to a metal constituting the metallic compound.

According to the embodiment, the seed particles and the metalliccompound may include silver.

According to the embodiment, the seed particles may include silverchloride.

According to the embodiment, a nano wire complex includes a metallicnano wire, and a seed particle bonded to the metallic nano wire. Theseed particle has a diameter in a range of 5 nm to 100 nm.

According to the embodiment, the seed particle is provided in themetallic nano wire or provided at one end of the metallic nano wire.

Advantageous Effects of Invention

As described above, according to the method of fabricating the nano wireof the embodiment, after forming the seed particles from the solvent,the metallic nano wire is formed by using the seed particles. In thiscase, according to the method of fabricating the nano wire of theembodiment, the diameter of the seed particles can be properly adjusted.For example, the seed particles may have a very small diameter of about5 nm to about 100 nm.

In this case, the metallic nano wire may be grown from the seedparticles. Since the seed particles have a very small diameter, themetallic nano wire may have very thin diameter.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a method of fabricating a nano wireaccording to the embodiment;

FIG. 2 is a view showing a nano wire complex according to theembodiment; and

FIG. 3 is a view showing another example of a nano wire complex.

MODE FOR THE INVENTION

A method of fabricating a nano wire of the embodiment includes a step offorming a plurality of seed particles by allowing first ions to react tosecond ions in a solvent and a step of forming a metallic nano wire byadding a metallic compound to the solvent and heating the solvent havingthe metallic compound added thereto.

In addition, the first ions may include metallic ions, and the secondions may include halogen ions.

In addition, the seed particles and the metallic compound may includethe same metal.

Further, the seed particles and the metallic compound may include silver(Ag).

In addition, the seed particles may include silver chloride (AgCl).

Besides, each seed particle may have a diameter of about 5 nm to about100 nm.

Hereinafter, the disclosure will be described in detail with referenceto accompanying drawings.

FIG. 1 is a flowchart chart showing the method of fabricating the nanowire according to the embodiment.

Referring to FIG. 1, a method for manufacturing a nano wire according tothe disclosure may include a step of heating a solvent (step ST10), astep of adding a capping agent to the solvent (step ST20), a step offorming a plurality of seed particles in the solvent (step ST30), a stepof adding a fourth metallic compound to the solvent (step ST40), a stepof adding a room-temperature solvent to the solvent (step ST50), and astep of refining a nano wire (step ST60). The steps are not essentialsteps, parts of the steps may not be performed according to themanufacturing method, and the sequence of the steps may be changed.Hereinafter, each step will be described in more detail.

According to the step of heating a solvent (step ST10), the solvent isheated at the reaction temperature suitable for forming the metallicnano wire.

The solvent may include polyol. The polyol serves as a mild reducingagent while serving as a solvent of mixing different materials, so thatthe polyol helps the formation of the metallic nano wire. For example,the polyol may include ethylene glycol (EG), propylene glycol (PG),glycerine, glycerol, or glucose. The reaction temperature may bevariously adjusted by taking the types and the characteristics ofsolvents and the metallic compounds into consideration.

For example, if a silver nano wire is formed by using propylene glycol(PG) representing superior reduction power as a solvent, the reactiontemperature may be in the range of about 80° C. to 140° C. If thereaction temperature is less than 80° C., the reaction speed is reduced,so that reaction may not smoothly occur, and the fabricating time may beincreased. If the reaction temperature exceeds 140° C., the silver nanowire may not be formed due to the aggregation phenomenon, and theproduct yield may be degraded.

As described above, according to the present embodiment, the silver nanowire may be fabricated at a reaction temperature lower than the reactiontemperature (e.g., 160° C.) according to the related art by usingpropylene glycol (PG) representing superior reduction power. Accordingto the related art, since the reaction temperature is high, silver nanowires having a short length (e.g., less than 5 μm), which isdisadvantageous when forming a network structure, may be formed, and theproduct yield of the silver nano wires may be lowered. In contrast,according to the present embodiment, silver nano wires having a lengthof 20 μm or more can be fabricated at a high product yield by reducingthe reaction temperature.

Thereafter, according to the step of adding the capping agent to thesolvent (step ST20), the capping agent inducing the forming of the wireis added to the solvent. If reduction for the forming of the nano wireis rapidly performed, metals are aggregated, so that the forming of thenano wire may be difficult. Accordingly, the capping agent prevents themetals from being aggregated by properly dispersing materials containedin the solvent.

The capping agent may include various materials. For example, thecapping agent may include material selected from the group consisting ofpolyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), cetyl trimethylammonium bromide (CTAB), cetyl trimethyl ammonium chloride (CTAC), andpolyacrylamide (PAA).

Then, according to the step of forming the seed particles in the solvent(step ST30), first and second metallic compounds are added to thesolvent. Accordingly, first ions contained in the first metalliccompounds may react to second ions contained in the second metalliccompounds, thereby forming the seed particles. In this case, the firstions may react to the second ions to form a third metallic compound, andthe seed particles may include the third metallic compound.

The first ions may include metallic ions. In more detail, the first ionsmay include gold ions, silver ions, platinum ions, or palladium ions

The second ions may include halogen ions. In more detail, the secondions may include chorine ions, bromide ions, or iodide ions.

In other words, the third metallic compound contained in the seedparticles may be expressed in following chemical formula 1.

Chemical Formula 1

MX

In this case, X represents Cl, Br, or I, and M represents Au, Ag, Pt, orPd.

The third metallic compound may have very low solubility with respect tothe solvent. Accordingly, the third metallic compound is extruded fromthe solvent and constitutes the seed particles.

The seed particles may have a very small diameter. The seed particlesmay have the diameter in the range of about 1 nm to about 1 μm. In moredetail, the seed particles may have the diameter in the range of about 5nm to about 100 nm. The above seed particles may be uniformly dispersedin the solvent.

The molar ratio of the second metallic compound to the first metalliccompound may be about 1:1. In addition, the first metallic compound maybe added to the solvent with the content of about 0.0001 wt % to about0.3 wt %. Further, the second metallic compound may be added to thesolvent with the content of about 0.0001wt % to about 0.3 wt %.

The first metallic compound may include salts including the first ions.In addition, the first metallic compound may include nitrates. In moredetail, the first metallic compound may include silver nitrate.

The second metallic compound may include salts including the secondions. In addition, the second metallic compound may include sodiumsalts. In more detail, the second metallic compound may include sodiumchloride.

Thereafter, in the step of adding a fourth metallic compound to thesolvent (step ST40), a reaction solution is prepared by adding thefourth metallic compound to the solvent.

In this case, the fourth metallic compound melt in an additional solventmay be added to a solvent having the capping agent added thereto and theseed particles provided therein. The additional solvent may include thesame material as that constituting an initial solvent or a materialdifferent from that constituting the initial solvent. In addition, thefourth metallic compound may be added after a predetermined time elapsesfrom time at which the seed particles are formed. Accordingly, thetemperature can be stabilized to a proper reaction temperature.

In this case, the fourth metallic compound may include metal used toform a metallic nano wire to be fabricated. In order to form silver nanowire, the metallic compound may include AgNO₃, or KAg(CN)₂.

As described above, if the fourth metallic compound is added to thesolvent including the capping agent and the seed particles, reactionoccurs so that the fabrication of the metallic nano wire is started. Inthis case, the metallic nano wire may be grown from the seed particles.In other words, metal extruded by reducing the fourth metallic compoundis grown from each seed particle to form the metallic nano wire.

In this case, since the seed particles have a very small diameter, themetallic nano wire may be grown with a small diameter.

After the metallic nano wire has been completely grown, the seedparticles may be removed through the following processes such as arefining process. In other words, in the following processes, the seedparticles may be separated from the metallic nano wire and removed.

However, a portion of the seed particles may remain. Accordingly, aportion of the third metallic compound may be detected from the metallicnano wire according to the present embodiment.

In other words, the seed particles may be bonded with the metallic nanowire thereby forming a nano wire complex.

FIG. 2 is a view showing the nano wire complex according to theembodiment. FIG. 3 is a view showing another nano wire complex.

As shown in FIGS. 2 and 3, portions of the metallic nano wire may havethe form a nano wire complex 10 or 11. The seed particles 100 are bondedwith the metallic nano wire 200. The ratio of the metallic nano wirerepresenting the form of the nano wire complex 10 or 11 may be about0.1% to about 0.001%.

In particular, as shown in FIG. 2, the seed particles 100 may beprovided at one end of the metallic nano wire 200. In addition, as shownin FIG. 3, seed particles 110 may be provided in the metallic nano wire200.

In this case, as described above, the diameters of the seed particles100 and 110 may be in the range of about 1 nm to about 1 μm, in moredetail, the range of about 5 nm to about 100 nm. In more detail, thediameters of the seed particles 110 and 110 may be in the range of about10 nm to about 50 nm. As described above, when the seed particles 100and 110 having a very small diameter are detected, the metallic nanowire having a small diameter is formed through the fabricating methodaccording to the present embodiment.

According to the present embodiment, 60 weight part to 330 weight partof the capping agent may be added based on 100 weight part of themetallic compound such as AgNO₃, or KAg(CN)₂. If less than 60 weightpart of the capping agent is added, the aggregation phenomenon can besufficiently prevented. If over 330 weight part of the capping agent isadded, metallic nano particles having a spherical shape or a cubic shapemay be formed, and the capping agent remains in the fabricated metallicnano wire, so that the electrical conductivity of the metallic nano wiremay be degraded.

In addition, the first and second metallic compounds may have thecontent in the range of 0.00001 weight part to 0.5 weight part based on100 weight part of the fourth metallic compound. If less than 0.00001weight part of the first and second metallic compounds is added, thereaction may not be sufficiently accelerated. In addition, if over 0.5weight part of the first and second metallic compounds is added, silveris rapidly reduced so that silver nano particles are generated or thenano wire may have a thick diameter and a short length. In addition,catalyst remains in the metallic nano wire so that the electricalconductivity may be degraded.

Thereafter, according to the step of adding the room-temperature solventto the solvent (step ST50), the room-temperature solvent is added to thesolvent in which reaction is started. The room-temperature solvent mayinclude a material identical to or different from a material used in theinitial stage. For example, the room-temperature solvent may includepolyol such as ethylene glycol and propylene glycol.

As the solvent, in which the reaction is started, is continuously heatedin order to maintain the constant reaction temperature, the temperaturemay be increased in the process of the reaction. As described above, thereaction temperature may be more constantly maintained by temporarilydegrading the temperature of the solvent by adding the room-temperaturesolvent to the solvent in which the reaction is started.

The step of adding the room-temperature solvent (step ST50) may beperformed one time or several times by taking the reaction time, and thetemperature of the reaction solution into consideration.

Thereafter, in the step of refining the nano wire (step ST60), themetallic nano wire is refined and collected in the reaction solution.

In more detail, if acetone serving as a non-polar solvent is added tothe reaction solution instead of water, the metallic nano wire isdeposited at the lower portion of the solution due to the capping agentremaining on the surface of the metallic nano wire. This is because thecapping agent is not dissolved in the acetone, but aggregated anddeposited although the capping agent is sufficiently dissolved in thesolvent. Thereafter, when the upper portion of the solution isdiscarded, a portion of the capping agent and nano particles arediscarded.

If distill water is added to the remaining solution, metallic nano wireand metallic nano particles are dispersed. In addition, if acetone ismore added, the metallic nano wire is deposited, and the metallic nanoparticles are dispersed in the upper portion of the solution.Thereafter, if the upper portion of the solution is discarded, a part ofthe capping agent and the aggregated metallic nano particles arediscarded. After collecting the metallic nano wire by repeatedlyperforming the above processes, the metallic nano wire is stored in thedistill water. The metallic nano wire can be prevented from beingre-aggregated by storing the metallic nano wire into the distill water.

As described above, according to the method of fabricating the metallicnano wire of the embodiment, the metallic nano wire is grown by usingseed particles having a very small diameter. Accordingly, the metallicnano wire having a small diameter can be formed.

EXPERIMENTAL EXAMPLE

200 ml of propylene glycol was heated at a temperature of 126° C., and6.7 g of polyvinylpyrrolidone and 0.1 g of potassium bromide were addedand melted. Thereafter, 0.35 mmol of sodium salt and 0.35 mmol of AgNO₃were added to form the seed particles. After about 10 mins were elapsed,2.3 g of AgNO₃ was melted in 100 ml of propylene glycol and added to asolution containing the polyvinylpyrrolidone and the seed particles.Then, the reaction was continued for about 2 hours, so that thefabrication of the silver nano wire was finished.

After the solution, which had been subject to the reaction, was dilutedby using 500 ml of acetone, 600 ml of acetone was added to the dilutedsolution. Then, the upper portion of the solution having propyleneglycol, and silver nano particles dispersed therein was discarded. Afterrepeatedly performing the above processes three times, the result wasstored in 10 ml of distill water.

COMPARATIVE EXAMPLE

Different from the experimental example, silver chloride particleshaving the average diameter of about 2.5 μm were added to the solventinstead of forming seed particles through the reaction between sodiumsalt and silver nitrate. Remaining procedures were performed in the samemanner as that of the experimental example.

Result

As shown in Table 1, a thinner and longer silver nano wire was formed inthe experimental example.

TABLE 1 average diameter(nm) average length(μm) Experimental Example 4522 Comparative Example 65 20

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A method of fabricating a nano wire, the method comprising: forming aplurality of seed particles by allowing a first ion to react with asecond ion in a solvent; and forming a metallic nano wire by adding andheating a metallic compound in the solvent.
 2. The method of claim 1,wherein the seed particles have a diameter in a range of 5 nm to 10nm.3. The method of claim 1, wherein the first ion is a metallic ion, andthe second ion is a halogen ion.
 4. The method of claim 1, wherein theseed particles include a metal equal to a metal constituting themetallic compound.
 5. The method of claim 1, wherein the seed particlesand the metallic compound include silver.
 6. The method of claim 1,wherein the seed particles include silver chloride.
 7. A nano wirecomplex comprising: a metallic nano wire; and a seed particle bondedwith the metallic nano wire, wherein the seed particle has a diameter ina range of 5 nm to 100 nm.
 8. The nano wire complex of claim 7, whereinthe seed particle is provided in the metallic nano wire.
 9. The nanowire complex of claim 7, wherein the seed particle is provided at oneend of the metallic nano wire.
 10. The nano wire complex of claim 7,wherein the seed particle includes chloride.
 11. The nano wire complexof claim 10, wherein the metallic nano wire includes silver, and theseed particle includes silver chloride.